Chromate production



Patented Jan. 10, 1956 f" GHRGMA-TE PRODUOTIQN .tMarvin J. Udy,Niagara'Ealls, N. Y.

- No Drawing. --'Application"May 12;19'49, Serial No. 92;9 51

14 Claims.

(This invention relates to chromate production eandi-has for an objectithe provision ofsandmproved process for :producingcalcium chroma-to.The invention furthercontemplates the provision ;of,;an improvedprocessvfor recovering chromium in: the-form of acalcium .chromate fromchromite eore,--chromitee0re concentrates;- altered chromite :zandsimilar chromium-bearing material.

iThroughout thespecification and in the claims,

s the term :ichromite oreriszintended to include '1 natural chromite:ore, altered chromite tore; :chro- :mite ore concentratesand similar.fchromite rmin- -:-:=.'eral':-.-bearing materials.

*According.;to;some? heretofore customary; practices, chromite ores.are'isubjected"togoxidizinglor.

roasting treatmentsin thexpresenceiiof zone or moreralkalirmetal'compoundsrsuch', for. example, -::-as isod-ium carbonate,sodiumyhydroxi'de and s0- i'diumzsulphateunder'such-conditions asztooxidize the trivalent chromium ofitthe chromite-orestozthe hexavalentstatezand produce'..,alkali metal .:chromates such,ifor exampleassodiumichromate. Sodium chromate thus .producedisseparated from fthe.product'of the roasting oroxidizing treatment by leaching andcrystallization andvmarketed" as H such. or converted to sodiumdichromateiforvimarketing. .Commercialsodium chromate 'and'sodiumzdichromate are utilized as raw or intermediate materialsin theproduction of oth'er'ichrominim-bearing compounds, including .vcalciumchromate. Usually,'the calcium chromateproduction operations arec-arriedout independently of the sodium chromate production-operations rand,consequently thesodium-'oxide content of thesodium chromate iswasted-orgat-anyrateis not I recovered in a" form in \r Which it -isreadily available for re-use:-in the chromate-iproduction roperations.:"For this reason, among othersg-calcium chromate is a relatively:costlwmaterial.

'Calcium chromate :is a :highly desirableirmateriala. Pier-:manyindustrialruses;- but its usefulness-has 7 not been :developed'ful'lybecause of'its highcost.

The present invention provides for theiproduc- :LtiOII 110i calcium.chromatezmnder conditionsiand g-aaccording'. togrprocedures suchtthatithensodiumi eoxidezcontent. .:of1 sodiunnchromate .zemployedninits productioni is'rut-ilizedmfomthe xrproductionnofiadditionalsodiumichromate.

- ifThefinvention-i utilizes :the:;.1teactions and .pro-

cicedures mfrthei-xammoniai soda; process; modified -:2by: substitution20f= ZSOdiUIIlLi-HltfatfiiiOIEI-Sfldill l'lliichloride,vimconjiunctionwith. a sodiumichrom'aite production-processxtoiiprovide' azcyolictprocessiior iLthezzproductionmnduleceveryoficalciumzehromaate JEIhe foregoing equations.illustitate-ztheprincipal BO-reactions. s Thei following eequationsmillustrateadditional reactions. involved in .the-tprocess Av completepreferrediprocess ofi-the invention acomprises 1)-treactingasodiumnitrate-and. :ammonium bicarbonate to producesodslumbicanbonuatesandammoniunnnitrate (-2) regenerating-the 3Oammonium rbicarbonate by sreactingi i the ammonium nit-ratewithzrcalciuml hydroxide with---..the

i DlKOdllCtlOHwOfeafiill'lIl'lOflifi andcalcium: nitrate. and --by:reactin ithe -ammoniawthus .iproduced-.--with zrcarbondioxidenimamaqneous:liquid,7(3) produc- 35 ingxcalcium chromateiandsimultaneously-regenerating the Y sodium i nitrateiibynreacting chromic:toxidea with theesodinmwroxidenofi the sodium ibinarbonate .z underzzoxidizing conditions nto .iorm 1sodiumlchromatezandereacting:thersodiunr chro- 4Q :mate 1 with the m'alciumivnitrate producedi-in,regenerating thezammoniun ebicarbonate;;(4lsepaaratingzthe"r-calcinmuchizomate' fromatheziqeg-enerated*isodiumiiiitratexand iw) :utllizing the-regen- 'eratedazsodiunnnitrateand; the :xgegenerated rammoniumibicarhbnatiaegeneratezasodiumusbicarbonatecionnseoinajzheizproduction poiadditional mcalciumchromate. As; inithe:operatioirzotithelammoniaasodamocs'ess employingsodium hloridemorproducevsodium '"50 bicarbonateasrianiendzcproduotgtherproduction iof "sodium: bicarbonatebyzreactiomofisodium anitrate andammoniumfbicazrbonatetpreferablyincludes 'the step for. aminoniationcof;the:solutionv containma thesubstitutedasndiunnmtmte the istepmf ewith regenenatiom'ofithezreagents; sodiumhitrzazteesa earbonatingcthwammdniatect fiolntionsuandmeparation of the solid sodium bicarbonate from the mother liquorin the usual manner. Regeneration of the ammonium bicarbonate preferablyincludes the ammonia recovery step of the ammonia soda process which, inthe modified process of the present invention, will result in theproduction of calcium nitrate, utilization of the ammonia in theammoniation of the sodium nitratecontaining solution and carbonation ofthe am-.- moniated solution, as in the ammonia soda process.

The sodium chromate producing phase of the calcium chromate productionand the sodium nitrate regeneration operation preferably is carried outin accordance with known procedures involving the roasting in air offinely divided chromite ore in the presence of available sodium oxide.The sodium oxide may be produced by employing sodium bicarbonatedirectly or by employing soda ash produced through decomposition of thesodium bicarbonate. The effect is the same whether sodium bicarbonate orsoda ash is employed. The sodium bicarbonate or soda ash is employed inamount sufficient to provide sodium oxide for combining with all of thechromium of the chromite ore when converted to the hexavalent state toform chromium trioxide. The sodium bicarbonate or soda ash is mixedintimately with the chromite ore of the roasting charge, and the chargeis heated to a temperature in the range 750 C. to 1100 C. In the courseof the heating operation in the presence of air, the sodium bicarbonateor soda ash is decomposed to form sodium oxide, the chromic oxide(CrzOs) of the chromite ore is oxidized to chromium trioxide (CrOz), andthe sodium oxide and the chromium trioxide react to produce sodiumchromate.

Sodium chromate is leached from the roasted or oxidized charge withwater in the usual manner to produce an aqueous solution. The aqueoussolution of sodium chromate may be employed directly in the calciumchromate production step, or the solution of sodium chromate may beconcentrated or evaporated to dryness to produce either a concentratedsolution or a solid product for use in the calcium chromate productionstep.

The sodium chromate preferably is added to the calciumnitrate-containing solution, which corresponds to the distiller wastesolution of the ammonia soda process, while the solution contains theheat absorbed in the distillation operation. The calciumnitrate-containing solution to which the sodium chromate is addedpreferably is heated to a temperature equivalent at least to the boilingtemperature at atmospheric pressure, and it preferably is heated to atemperature in the range, 120 C. to 135 0., under a pressure in therange, 15 to 30 pounds per square inch, to effect precipitation of theanhydrous calcium chromate. At temperatures and pressures in the rangesindicated, precipitation of calcium chromate is virtually complete.Complete removal of the calcium chromate is not essential to the economyof the process, as the of a sodium bicarbonate product for marketingmother liquor from the precipitation treatment is to be recycled toregenerate sodium bicarbonate, and chromate remaining therein will notinterfere with the reactions involved in the: ammonia soda process. Thechromate will remain in the system without loss. When equilibrium hasbeen established, calcium-chromate equivalent to the sodium chromateemployedwill be obtained at a uniform rate. The advantage reas such,dilution Water may be introduced at two points, namely, at the filtersas wash water for the sodium bicarbonate, and in the distiller in theform of milk of lime. In the process of the invention, washing of thesodium bicarbonate at the filters is unnecessary because the crudeprodnot can be employed directly in the sodium chromate production step,and, if desired, the lime may be added in the solid state to thedistillers to avoid the introduction of water into the system. In theprocess of the invention, diluent water may be added with sodiumchromate, but addition at this point can be avoided by employing sodiumchromate in the form of a solid. If the addition of diluent'waterthrough washing and reagent addition is eliminated completely, it willbe necessary to add make-up water to compensate for evaporation. In anyevent the functioning of the process of the invention can be socontrolled that evaporation costs Will be slight or even negligible.

The combined use of the principles and reactions of the ammonia sodaprocess and the principles and reactions of the calcium chromateproduction process permits the achievement of the following advantagesamong others:

(1) It permits the re-use of the source of sodium which, according tothe present invention, is sodium nitrate with a saving in cost of rawmaterials, a saving in the cost of preparing and purifying the source ofsodium and with the establishment of more uniform conditions leading togreater efiiciency through the use of a source of sodium of the samecomposition in all ammoniation and carbonation operations.

(2) It permits the saving and utilization in the production of the endproduct of the combined process of the calcium normally wasted as calcium chloride.

(3) It conserves the heat of the distiller waste solution which normallyis dissipated without accomplishing a useful result or is usedinefliciently, and it permits utilization of the heat directly in theproduction of the end product of the combined process.

(4) It permits a saving in labor and equipment costs by permittingelimination of washing of the sodium bicarbonate at the filters.

I claim:

1. A cyclic process for producing calcium chromate which comprises (1)reacting sodium nitrate and ammonium bicarbonate to produce sodiumbicarbonate and ammonium nitrate, (2) regenerating the ammoniumbicarbonate by react ing the ammonium nitrate with ,calcium hydroxidewith the production of ammonia and calcium nitrate and reacting theammonia thus produced with carbon dioxide in an aqueous liquid, (3)producing calcium chromate and simultaneously regenerating the sodiumnitrate by reactlng chromic oxide with the sodium oxide of the arsenicsodium bicarbonate under oxidizing conditionsrto form sodiumchromateandreacting the-sodium chromate:v with calcium. nitrateproduced. in re; generating theiammoniumbicarbonate. (a) sepra+ratingthe calcium chromate frQmJthe regenerated sodium chloride, and. 5utilizingthe regenerated sodium nitrate and the regenerated ammoniumbicarbonate to: regenerate sodiumbicarbonate for use in the productionof additional calcium chromate.

2. A cyclic process. for producing calcium chromatei which comprises (10reacting sodium nitrate and ammonium bicarbonate. in; aqueous solutionto produce sodium bicarbonate andam, monium nitrate, (2) regeneratingtheram-monium bicarbonate by reacting the. ammonium nitrate with calciumhydroxide in aqueous. solution with the production of ammonia andcalcium nitrate and reacting the ammonia thus: produced carbon dioxide.in an aqueous liquid, (3:) producing calcium chromate and simultaneouslyregenerating the sodium nitrate by reacting. chromic oxide with thesodium oxide of the sodium: bi.- carbonateunder oxidizingconditions-to.- fornrsoid-i-um chromate and reacting the.sodium'chromate' with calcium nitrate produced in regenerating theammonium bicarbonate at an elevated? ternperature, Oi)- separati-n-g'thecalcium .chromate r'i'om the. regenerated sodium chloride, and ('5);utilizing the regenerated sodium nitrate and: the regenerated ammoniumbicarbonate tov regenerate sodium bicarbonate for use in the productionof additional calcium chromate.

3. A cyclic process for producing calcium chromate which comprises (1)reacting sodium nitrate and ammonium bicarbonate in aqueous solution toproduce sodiumbicarbonate and'ammonium nitrate; (2) regenerating theammonium bicarbonate by reacting the ammonium nitrate with calciumhydroxide in aqueous'sol ution with the production of ammonia andcalcium nitrate and reacting the ammonia thus produced with carbondioxide in an aqueous liquid; (3). producing calcium chromate andsimultaneously regenerating the sodium? nitrate by reacting chromicoxide with the sodium oxidev of the sodium bicarbonate under: oxidizingconditions to form sodium chromate and? reacting the sodium chromatewith calcium nitrate produced in: regenerating the am monium bicarbonatein aqueous solution at a carbon dioxide in an aqueous. liquid; ('33.produc=- ing calcium. chromate and simultaneously regeneratingthe sodiumnitrate by reacting chromic oxide with the: sodium oxide of the sodiumbifcarbonate under oxidizingconditions. to form see dium chrcmate and.reacting'the sodium chromate with calcium nitrate produced in.regenerating.

the. ammonium. bicarbonate. in aqueous. solution underpressureata-temperature abnrelno ci, (41):

(iii.

.itt.

separating the chromate from: the. re.'-' 75 6 generated sodiumznitrate;and: (5) utiiizingrrthe regenerated: sodium; nitrate: and. the;regenerated ammonium bicarbonate: to: regenerate SQdiHmZbiecarbcnate'fci: use .imthe. production of additional calciumchromate.

5; A; cyclic.- processfor: producing calcium chromate; which comprises(.1) reacting sodium nitrate; and ammonium bicarbonate aqueous solutionto produce sodium bicarbonate and; ammcniimi nitrate; .(12').regenerating the. ammonium bicarbonate. by reacting the ammonium nitratewith .caiciunrhydroxide in; aqueous solution with the production of;ammonia and calcium nitrate and reacting'the ammoniathus produced: withcarbon dioxide inarraqneous liquid, (.3 producing calcium chromate: andsimultaneously regenerate ing thesodiunr nitrateby reacting: chromicoxide withthe sodiumoxide of. the sodium bicarbonateunderioxidizingconditions to form sodiumchromate andreacting the: sodiumchroma-to with calciumnitrate producedain regenerating the ammoniumbicarbonate. in aqueous solution under pressure above 15- pounds: persquare inch at a temperature'abore120C, (4) separating the-cal cium'chromatefrom. theregeneratedisodium ni'- trate, and (5 utilizing'the.regenerated sodium nitrate: and the: regenerated ammonium bicar bonateto: regeneratetsodium bicarbonate for use in the production ofadditfonalcalcium chromate.

GMA. cyclic process; for producing calcium chromatewhiclr comprises (1.)reacting sodium nitrate: and ammonium bicarbonate in aqueous solution.to prodncevsodium bicarbonate. and ammoniumsnitrate, (.2): regeneratingthe ammonium bicarbcnateby" reacting the ammonium nitrate withcalcinm'hydroxiderirr aqueous. solution with the production or: ammonia andcalcium nitrate reacting the: ammonia thus produced with carbon dioxidein. arraqueous liquid, (3 producing calcium chromate and simultaneouslyregencratingthesodium nitrate by reacting chromic oxide' witlrthesodium: oxide. of the sodium: bicarbonate und'en oxidizing conditions toform sochrom-atei and; reacting: the. sodium chromater withcalciimrnitrateproduced regenerat ing the ammonium bicarbonate. in aqueoussolutionundcr'rpressureatatemperature in the range 120 C to 1355" (1.,(c). separating the calcium chromatefrom the regenerated. sodiumnitrate, and-(.5)? utilizing: the regenerated sodium nitrate andtherregenerated ammonium bicarbonate to regeneratesodium bicarbonate for usein the prodnction. of additional calcium chromate.

7:...A cyclic; process for producing calcium chromate which comprises61) reacting sodium ni-' trate and ammonium. bicarbonate in aqueoussolutionzto produce? sodium. bicarbonate and ammonium nitrate, (2)-regenerating". the ammonium bicarbonate by reacting the ammonium nitratewith calciinnzhyd-roaride aqueous solution with the; production of:ammonia and calcium nitrate and reacting the ammonia thus produced withcarbon dioxide in an aqueous liquid, (3 producing calcium chromatesandt'simultaneously regeneratthesodium nitrate by reacting chromicoxide the.sodiumaoxideof the. sodium bicarbonate under; oxidizing conditions. to:form: sodium chr0 mate and reacting the. sodium chromatewith calciumnitrate produced in regenerating the ammoninmbicarbonate in.aqueoussolution under pressurethe range: 15 try-3.0 pounds per squareinch, at. a. temperature in the. range, 129 C to 1&5?" El, ((41).separating the: calcium: ch-romate from. sodium: nitrate; and. (5i?utilizing: the; regenerated sodiumpniinzate an di the regeneratedammomurmbicarbonat to regenerate sodium bicarbonate for use in theproductionof additional calcium chromate; 8. A cyclic process forproducing calicum chromate which comprises (1) reacting sodium nitrateand. ammonium bicarbonate to produce sodium bicarbonate and ammoniumnitrate; (2) regenerating the ammonium bicarbonate by reacting theammonium nitrate with calcium -:hydroxide with the production of ammoniaand calcium nitrate and reacting the ammonia thus produced with carbondioxide in an aqueous liquid (3) producing calcium chromate andsimultaneously regenerating the sodium nitrate by reacting chromic oxidewith the sodium oxide of the sodium bicarbonate under oxidizingconditions to form sodium chromate and reacting the sodium chro-i matewith calcium nitrate produced in regener' ating the ammoniumbicarbonate, (4) separating the calcium chromate from the regeneratedsodium nitrate, and (5;) utilizing the'regenerated sodium nitrate andthe regenerated ammonium bicarbonate to regenerate sodium bicarbonatefor use in the production of additional calcium chromate, the reactionbetween chromic oxide and the sodium oxide of the bicarbonate beingeffected by roasting a mixture comprising chromite ore and the sodiumoxide in air at a temperature in the range 750 C. to 1100 C.

9. A cyclic process for producing calcium chromate which comprises (1)reacting sodium nitrate and ammonium bicarbonate in aqueous-solution toproduce sodium bicarbonate and ammonium nitrate, (2) regenerating-theammonium bicar' bonate by reacting the ammonium'nitrate with calciumhydroxide in aqueous s'olu'tion'with the production'of ammonia andcalcium nitrate and reacting the ammonia thus produced with carbondioxide in an aqueous liquid, (3) producing cal-- cium chromate andsimultaneouslyregenerating the sodium nitrate by reacting chromic oxide"with the sodium oxide of the sodium bicarbonate under oxidizingconditions to form sodium chromate and reacting the sodium chromate withcalcium nitrate produced in regenerating the ammonium bicarbonate at anelevated temperature i) sep arating the calcium chromate from theregenerated sodium nitrate, and (5) utilizing the regenerated sodiumnitrate and the regenerated ammonium bicarbonate to regenerate sodiumbicarbonate for use in the production of additional" calcium chromate,the reaction between chromic oxide and the sodium oxide' of the"bicarbonate being eiiected by roasting a mixture comprising chromiteore and the sodium oxide in air at a temperature in the range 750 C. to1100 C.

10. A cyclic process for producing calcium chromate which comprises (1)reacting sodium nitrate and ammonium bicarbonate in aqueous solution toproduce sodium bicarbonate and ammonium nitrate, (2) regenerating theammonium bicarbonate by reacting the ammonium nitrate with calciumhydroxide in aqueous solution with the production of ammonia and calciumnitrate and reacting the ammonia-thus produced with carbon dioxide in anaqueous liquid, v,(3) producing calcium chromate andsimultaneously;regenerating the sodium nitrate by reactingchromic oxidewith the sodium oxide of the sodium bicarbonate under oxidizingconditions to form sodium chromate and reacting the sodium chromate withcalcium nitrate produced in regenerating the ammonium bicarbonate inaqueous solution at a boiling temperature (4') separating the calciumchromate from the'regeneratedsodium-nitrate, and (5) utilizing theregenerated sodium nitrate and the regenerated ammonium bicarbonate toregenerate sodium bicarbonate for use in the production of additionalcalcium chromate, the reaction between chromic oxide and the sodiumoxide of the bicarbonate being efiected by roasting a mixture comprisingchromite ore and the sodium oxide in air at a temperature in the range750 C. to 1100 C. Y

11. A cyclic process for producing calcium chr0- mate which comprises(1) reacting sodium nitrate and ammonium bicarbonate in aqueous solutionto produce sodium bicarbonate and ammonium ni-, trate, (2) regeneratingthe ammonium bicarbonate by reacting the ammonium nitrate with cal-.cium hydroxide in aqueous solution with the production of ammonia andcalcium nitrate and reacting the ammonia thus produced with carbondioxide in an aqueous liquid, (3) producing calcium chromate andsimultaneously regenerating the sodium nitrate by reacting chromic oxidewith the sodium oxide of the sodium bicarbonate under oxidizingconditions to form sodium chromate and reacting the sodium chromate withcalcium nitrate produced in regenerating the ammonium bicarbonate inaqueous solution under pressure at a temperature above C., (4)separating the calcium chromate from the regenerated so-- dium nitrate,and (5) utilizing the regenerated sodium nitrate and the regeneratedammonium bicarbonate to regenerate sodium bicarbonate for use in theproduction of additional calcium chr0- mate, the reaction betweenchromic oxide and. the sodium oxide of the bicarbonate being effected byroasting a mixture comprising chromite ore and the sodium oxide in airat a temperature in the range 750 C. to 1100 C.

12. A cyclic process for producing calcium chromate which comprises (1)reacting sodium nitrate and ammonium bicarbonate in aqueous solution toproduce sodium bicarbonate and ammonium nitrate, (2) regenerating theammonium bicarbonate by reacting the ammonium nitrate with calciumhydroxide in aqueous solution with the production of ammonia and calciumnitrate and re: acting the ammonia thus produced with carbon dioxide inan aqueous liquid, (3) producing calcium chromate and simultaneouslyregenerating the sodium nitrate by reacting chromic oxide with thesodium oxide of the sodium bicarbonate under oxidizing conditions toform sodium chromate and reactin the sodium chromate with calciumnitrate produced in regenerating the ammonium bicarbonate in aqueoussolution under pressure.

above 15 pounds per square inch at a temperature above C., (4)separating the calcium chromate from the regenerated sodium nitrate, and(5) utilizing the regenerated sodium nitrate and the regeneratedammonium bicarbonate to regenerate sodium bicarbonate for use inmatewhich comprises (1) reacting sodium nitrateand ammonium bicarbonate inaqueou's'solution to produce sodium bicarbonate and ammonium nitrate,(2) regenerating the ammonium bicarbon ate by reacting the ammoniumnitrate with calcium hydroxide in aqueous solution with the productionof. ammonia and calcium nitrate and re- 75 actingtheammoniaithusproduced'with carbondioxide in an aqueous liquid, (3) producin calciumchromate and simultaneously regenerat ing the sodium nitrate by reactingchromic oxide with the sodium oxide of the sodium bicarbonate underoxidizing conditions to form sodium chromate and reacting the sodiumchromate with calcium nitrate produced in regenerating the ammoniumbicarbonate in aqueous solution under pressure at a temperature in therange 120 C. to 135 C., (4) separating the calcium chromate from theregenerated sodium nitrate, and (5.) utilizing the regenerated sodiumnitrate and the regenerated ammonium bicarbonate to regenerate sodiumbicarbonate for use in the production of additional calcium chromate,the reaction between chromic oxide and the sodium oxide ofithebicarbonate being efiected by roasting a mixture comprising chromite oreand the sodium oxide in air at a temperature in the range 750 C; to 1100C.

14. A cyclic process for producing calcium chromate which comprises (1)reacting sodium nitrate and ammonium bicarbonate in aqueous solution toproduce sodium bicarbonate and ammoniu-m nitrate, (2) regenerating theammonium bicarbonate by reacting the ammonium nitrate with calciumhydroxide in aqueous sol-utioniwith the production of ammonia andcalcium nitrate and reacting the ammonia thus produced ;with carbondioxide in an aqueous liquid, (3) producing calcium chromate andsimultaneously regencrating the sodium nitrate by reacting chromic oxidewith the sodium oxide Of the sodium bicarbonate under oxidizingconditions to form sodium chromate and reacting the sodium chromate withcalcium nitrate produced in regenerating the ammonium bicarbonate inaqueous solution under pressure in the range of 15 to' pounds per Squareinch, at a temperature in the range, C. to 0., (4) separating thecalcium chromate from the regenerated sodium nitrate, and (5) utilizingthe regenerated sodium nitrate and the regenerated ammonium bicarbonateto regenerate sodium bicarbonate for use in the production of additionalcalcium chromate, the reaction between chromic oxide and the sodi-umoxide of the bicarbonate being efiected by roasting a mixture comprisingchromite ore and the sodium oxide in air at a temperature in the range750 C. to 1100" C.

MARVIN J. UDY.

REFERENCES CITED The following references are of record in the file ofthis patenlt:

UNITED STATES PATENTS Number Name Date 200,134 Fahlberg Feb. 12, 18781,955,326 Demant Apr. 17, 1934 2,368,481 MacColl Jan. 30, 1945 2,402,103Udy June 11, 1946 OTHER REFERENCES How, Manufacture of Soda," TheChemical Catalog Co., Inc., 330 West 42nd St., New York City (1933).

1. A CYCLIC PROCESS FOR PRODUCING CALCIUM CHROMATE WHICH COMPRISES (1)REACTING SODIUM NITRATE AND AMMONIUM BICARBONATE TO PRODUCE SODIUMBICARBONATE AND AMMONIUM NITRATE, (2) REGENERATING THE AMMONIUMBICARBONATE BY REACTING THE AMMONIUM NITRATE WITH CALCIUM HYDROXIDE WITHTHE PRODUCTION OF AMMONIA AND CALCIUM NITRATE AND REACTING THE AMMONIATHUS PRODUCED WITH CARBON DIOXIDE IN AN AQUEOUS LIQUID, (3) PRODUCINGCALCIUM CHROMATE AND SIMULTANEOUSLY REGENERATING THE SODIUM NITRATE BYREACTING CHROMIC OXIDE WITH THE SODIUM OXIDE OF THE SODIUM BICARBONATEUNDER OXIDIZING CONDITIONS TO FORM SODIUM CHROMATE AND REACTING THESODIUM CHROMATE WITH CALCIUM NITRATE PRODUCED IN REGENERATING THEAMMONIUM BICARBONATE, (4) SEPARATING THE CALCIUM CHROMATE FROM THEREGENERATED SODIUM CHLORIDE, AND (5) UTILIZING UTILIZING REGENERATEDSODIUM NITRATE AND THE REGENERATED AMMONIUM BICARBONATE TO REGENERATESODIUM BICARBONATE FOR USE IN THE PRODUCTION OF ADDITIONAL CALCIUMCHROMATE.